IEC 61828:2001

INTERNATIONAL IEC
STANDARD
First edition
2001-05
Ultrasonics – Focusing transducers –
Definitions and measurement methods
for the transmitted fields
Ultrasons – Transducteurs focaliseurs –
Définitions et méthodes de mesure
des champs transmis
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INTERNATIONAL IEC
STANDARD
First edition
2001-05
Ultrasonics – Focusing transducers –
Definitions and measurement methods
for the transmitted fields
Ultrasons – Transducteurs focaliseurs –
Définitions et méthodes de mesure
des champs transmis
 IEC 2001  Copyright - all rights reserved
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– 2 – 61828 © IEC:2001(E)
CONTENTS
FOREWORD.4

INTRODUCTION.5

1 Scope.6

2 Normative references .6

3 General .7

3.1 Focusing transducers .7

3.1.1 Focusing methods .7
3.1.2 Known and unknown focusing transducers .7
3.1.3 Focusing and beamwidth .8
3.1.4 New focusing parameter definitions .8
3.1.5 Applications of focusing definitions .9
3.1.6 Relation of present definitions to physiotherapy transducers (treatment heads).9
3.2 System and measurement requirements.9
3.2.1 Transmitted pressure waveforms .9
3.2.2 Radiated fields .9
3.3 General focused field descriptions.10
3.3.1 General field descriptions for transducers of known construction .10
3.3.2 The scan plane and the steering of beams.11
4 Focusing definitions.12
4.1 Background information.12
4.2 Definitions .12
5 List of symbols .23
6 Measurement procedures .24
6.1 General .24
6.1.1 Set-up .25
6.2 Finding the beam axis .25
6.3 Determining if transducer is focusing.27
6.4 Measuring other focal parameters of a focusing transducer .28
Annex A (informative) Background for the transmission/Characteristics

of focusing transducers.38
Annex B (informative) Methods for determining the beam axis for well-behaved beams .43
Annex C (informative) Methods for determining the beam axis for beams that
are not well-behaved.47
Bibliography.49

61828 © IEC:2001(E) – 3 –
Figure 1 – Transducer options – Top: Transducer with a radius of curvature R and a focal

length equal to R – Middle: Transducer with a plano-concave lens – Bottom: Transducer

with a plano-convex lens.29

Figure 2 – Definitions for focusing measurements when the transducer geometry is

unknown .30

Figure 3 – Field parameters for non-focusing and focusing transducers .31

Figure 4 – Beam contour plot – Contours at –6, –12, and –20 dB for a 5 MHz transducer

with a diameter of 25 mm and a radius of curvature of 50 mm centred at location 0,0
(bottom centre of graph) .32

Figure 5 – Parameters for describing a focusing transducer of a known geometry.33

Figure 6 – Path difference parameters for describing a focusing transducer of a known
geometry .34
Figure 7 – Beamwidth focus in a principal longitudinal plane.35
Figure 8 –Types of geometric focusing.36
Figure 9 – Pressure focus in a principal longitudinal plane.37
Figure B.1 – X-axis scan at 9 cm depth for the first focal zone with beam centre.44
Figure B.2 – X-axis scan at 4,4 cm depth for the second focal zone.45
Figure C.1 – Asymmetric beam showing beamwidth midpoint method .48
Table B.1 – Standard deviations for x and y scans using three methods of determining
the centre of the beam .43
Table B.2 – –dB beamwidth levels for determining midpoints .46

– 4 – 61828 © IEC:2001(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
ULTRASONICS – FOCUSING TRANSDUCERS –

DEFINITIONS AND MEASUREMENT METHODS

FOR THE TRANSMITTED FIELDS
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International
Organization for Standardization (ISO) in accordance with conditions determined by agreement between the
two organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61828 has been prepared by IEC technical committee 87:
Ultrasonics.
The text of this standard is based on the following documents:
FDIS Report on voting
87/196/FDIS 87/204/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 3.
Annexes A, B and C are for information only.
The committee has decided that the contents of this publication will remain unchanged
until 2005. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
61828 © IEC:2001(E) – 5 –
INTRODUCTION
Focusing transducers are essential in medical applications for obtaining high-resolution

images, Doppler and flow data and for concentrating ultrasonic energy at desired sites for

therapy. Present terminology for focusing transducers is inadequate for communicating

precisely the characteristics of the focused fields of the wide variety of transducers and

transducer array types and focusing means in common usage.

This International Standard provides specific definitions appropriate for describing the

focused field from a theoretical viewpoint for transducers with known characteristics intended

by design. Other specific definitions included in this standard, based on measurement

methods, provide a means of determining focusing properties, if any, of a transducer of
unknown field characteristics. The measurement method and definitions provide criteria for
determining if the transducer is focusing, as well as a means of describing the focusing
properties of the field. Beam axis alignment methods are given for focusing transducers.

– 6 – 61828 © IEC:2001(E)
ULTRASONICS – FOCUSING TRANSDUCERS –

DEFINITIONS AND MEASUREMENT METHODS

FOR THE TRANSMITTED FIELDS
1 Scope
This International Standard
− provides definitions for the transmitted field characteristics of focusing transducers for
applications in medical ultrasound;
− relates these definitions to theoretical descriptions, design, and measurement of the
transmitted fields of focusing transducers;
− gives measurement methods for obtaining defined characteristics of focusing transducers;
− specifies beam axis alignment methods appropriate for focusing transducers.
This International Standard relates to focusing ultrasonic transducers operating in the
frequency range appropriate to medical ultrasound (0,5 MHz to 40 MHz) for both therapeutic
and diagnostic applications. It shows how the characteristics of the transmitted field of
transducers may be described from the point of view of design, as well as measured by
someone with no prior knowledge of the construction details of a particular device. The
radiated ultrasound field for a specified excitation is measured by a hydrophone in either a
standard test medium (for example, water) or in a given medium. The standard applies only to
media where the
...